If your soy protein is the kind of crumbles that are ready to use, you can use them with a shorter cooking time. If you have some kind of TVP (dry) it would need to be soaked first, or you will need to add a little water to the sauce, then cook for a short time before adding the sauce. You will also have less fat from the soy, so you could add a little more oil, according to your taste and judgement.